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Monday, August 05, 2013

The Things That Didn’t Happen To Flight 214

Just moments before Asiana Airlines Flight 214 was to land
at the San Francisco International Airport on July 6, some passengers noticed
that backdraft from the jet engines was kicking up seawater.This usually doesn’t happen on normal
approaches to Runway 28L, which extends from just behind a seawall that faces
San Francisco Bay onto land.A few
seconds later, the main landing gear hit the seawall and sheared off.After that impact, both engines and the
tail section came off, carrying some passengers and crew with it.The main fuselage slammed into the
runway and spun almost completely around before grinding to a halt.

Flight attendants sprang into action, assisting passengers
who needed help in exiting the aircraft.One injured girl was pulled from the plane by a first responder, only to
be covered in firefighting foam from arriving fire trucks.Sadly, another emergency vehicle’s
driver failed to see her underneath the foam, and she was struck and killed.Another passenger died at the scene and
a third passed away a few days later from injuries.All of the other 304 people aboard survived, including all the
pilots and crew, although some sustained serious injuries.After the plane was evacuated, a fire
from an oil leak demolished much of the fuselage, but without injuring anyone.

Any fatal accident involving air travel is a
tragedy—usually an avoidable one.But this accident could have been much worse, and that fact carries with
it some implicit good news.

For one thing, the Boeing 777 involved is a model that was
introduced in 1995, and this 2013 accident is the first one involving loss of passenger
lives in a flight-related accident.Although fatal accidents have occurred earlier, they involved refueling
or other ground-based situations.This is an outstanding safety record compared to planes developed during
the earlier years of aviation.

Another fact worth noting is that the landing gear was
purposely designed to break away under a sufficiently large impact, rather than
staying attached to cause a destructive nosedive.We are familiar with breakaway traffic signs on highways,
but I wasn’t aware until now that the same principle has been designed into
landing gear.

Finally, the fact that the fuselage endured the abuse of
skidding thousands of feet down the runway sans landing gear and kept the
remaining fuel from catching fire, staying together long enough for everyone to
escape, is a testimonial to its structural engineering.I am no mechanical engineer, but
somebody did something right to make a fuselage that would hang in there during
such a trial.

There are things that no airframe can endure, of
course.If the plane had
encountered a large immovable object, for example, the outcome might have been
quite different.A similar
accident in some ways to the Asiana Airlines crash took place on August 2,
1985.A Delta Airlines Lockheed
L-1011 with 163 people on board was caught in a microburst and windshear during
a thunderstorm at the Dallas-Fort Worth Airport during its final landing
approach.The sudden loss of
airspeed and accompanying downdraft forced the plane to the ground north of the
runway, where it skidded into some giant water tanks and exploded.Only 26 people survived.Windshear detectors have since been
installed at many airports, and pilots are much more aware of the dangers of
such conditions, so the cause of that particular crash is much less likely to
occur these days.

The cause of the Asiana crash is still under
investigation, but attention has been focused on the flight crew, which
consisted of three captains and a first officer.The man actually flying the plane at the time of the crash
had less than fifty hours’ experience on 777s, and was being instructed by the
pilot in command, who occupied the co-pilot’s seat at the time.The runway’s instrument landing system (ILS)
vertical glide slope was out of service and a notice had been issued to that
effect.This made it impossible to
execute an ILS landing to the runway.Records indicate that the various automated landing-assistance systems
were manipulated during the approach, and it may not have been clear to the
flight crew that their approach was too low and slow until it was too late to
do anything about it.The laws of
inertia are always in force, and a lot of advance planning has to be done to
bring a huge heavy object like a 777 in contact with the ground safely.Although final conclusions will have to
await the completion of the ongoing investigations, it appears that pilot error
may be at the bottom of this accident.

As long as human pilots fly planes, we will always have to
contend with the possibility of pilot error.But in general, air travel is safer now than it has ever
been, in terms of fatalities per passenger-mile flown.Even the absolute numbers of fatalities
per year, which obviously stood at zero until the invention of the airplane,
continues a downward trend that began in the 1970s, and is the lowest since about
1954.And the total number of
passenger-miles flown in 1950 was only about 2% of what it was in 1990.

The Asiana crash may have stemmed from confusion about who
was in charge—the autopilot mechanisms or the real pilot.But for the vast majority of planes and
flights, the amazing system of man and machine called air travel operates
efficiently, economically, and with a safety record that was unimaginable in
the early days of flight.

Sources:I referred to the Wikipedia articles on
“Asiana Airlines Flight 214,” “Delta Airlines Flight 191,” “USAirways Flight
1549,” and “Aviation safety.”I
also obtained statistics on air travel safety from a paper by Prof. Dan Bogart
of UC Irvine which can be found at http://www.socsci.uci.edu/~dbogart/transport_momentusBogart_6.11.12.pdf.

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